Thread: Suggestions please: Accurate hole drilling

I would nail down 2 small strips at 90 degrees on top of a piece of board and clamp it to your drill press (if you have one) don't make the strips touch together at the 90, leave a small gap so you can get the swarf out easier.

Dave

Lou,
If your "home made" setup includes a jig and you are still getting inaccurate results, then maybe your drill bit is wandering. Maybe try a centre drill?
Chris

I would make a jig consisting of a sheet of plywood, with two short strips of flat 10 x 3 attached Northeast of the hole location, to form stops. Clamp the jig to the drill press table, and make some test holes to establish exact position for final clamping. Assuming the other end of the workpiece is similar, make the plywood large enough to support that end.

The reason for the Northeast location of the stops is so you hold the workpiece in your left hand, and operate the drill press with your right hand (unless you have a left-hand drill press, in which case reverse to Northwest). Leave the drill running continuously.

If you expect to interrupt for other use of the drill press, make the plywood short in the North and East directions, and mark the drill press table to assist resetting for future batches.

In lieu of clamps, you could also use two bolts through the slots in the drill press table.

Cheers,
Joe

Originally Posted by jack620

Lou,
If your "home made" setup includes a jig and you are still getting inaccurate results, then maybe your drill bit is wandering. Maybe try a centre drill?
Chris

Hello Jack,

those centre drills might solve the problem. I'll see if I can buy one locally and try it.

Guys, I do have a jig made up for the job but the problem seems to be the 'play' in the drop-down shaft in the drill press.

A friend suggested a "gear driven' drill press would not have any play in the drop-down shaft, is this correct?

Another friend suggested I should get a small lathe that accepts a drill chuck!

The ultimate idea is to have a dedicated tool set up just for drilling that hole accurately that anyone can use without any machanical expertise.

Regards,
Lou

Are you centre-punching before drilling? With Aluminium you should be able to get a nice deep punch mark that will locate a 6mm drill. If you do that and use a good sharp drill you may not even need a jig.

lol I cant understand your friends reasoning its just way to over the top.

Are you running your drill at the right speed? 6mm HSS drill in aluminum should be run about 2,600 rpm so use the fastest speed you can.

Is your drill sharpened properly with a 118deg point? I would recommend thinning the point web to make it as sharp as possible

Have a squirt bottle of water to keep the drill cool. Move the table up as far up as you can to reduce flex in the quill and you should be sweet

If all this doesnt work you could go one step further and get a short serious drill, they are about half the length of standard drills

Originally Posted by Bryan

Are you centre-punching before drilling? With Aluminium you should be able to get a nice deep punch mark that will locate a 6mm drill. If you do that and use a good sharp drill you may not even need a jig.

Hello Bryan,

having to centre puch and then drill would be too slow and cumbersome, vertually double handling. OK for a few holes but not 300 (and hopefully more as sales pick up!)

And of course you would still have the problem of making sure that the centre punch mark was in exactly the right spot on the bar.

Think more on the lines of a production line; place the aluminium in a jig and pull the handle to drill so to speak.

rehards,
Lou

If you don't punch it and your quill is sloppy the drill will wander, even with the best jig in the world. IMHO.

If you are going to use a centre drill you would be double handling the Aluminium strip.
I would be inclined to make a jig from steel or Aluminium rather than ply with a hardened drill guide which would have the 6mm hole in it, something similar should be available from your local engineering supply company. That way, once set up no matter how much play was in the drill press quill it would still drill on centre every time. Also bolting the jig to the drill press helps a lot.
I used to manufacture fridge slides in Adelaide for Engel (150 units(1200holes) at a time)and other fridges and this is the system I used, the holes were tapped after, so I found it a very accurate way of doing them.
Regards
Kryn
(Ex Australian 4WD Storage Systems and Accessories)

Hello KB,
Thank you for your reply.

Originally Posted by KBs PensNmore

If you are going to use a centre drill you would be double handling the Aluminium strip.

Yes I came to that conclusion after googling the centre drills.

.... a hardened drill guide which would have the 6mm hole in it, something similar should be available from your local engineering supply company. That way, once set up no matter how much play was in the drill press quill it would still drill on centre every time.

A hardened drill guide sounds good.
Don't know how I'll go trying to buy one where I live but will certainly look for one on the net.

Also bolting the jig to the drill press helps a lot.

Yep, done that.

Regards,
Lou

With a decent drill press, a fence and a stop you should be able to set up for spot on, and get accurate repeatable results. However you suggest that your drill press spindle wanders. This is a common condition with many cheapo drill presses, caused by poor machining of the spindle bore in the head casting.

Your friends suggestion of a geared head drill has some merit, probably indirectly. There are two factors involved there, the first is that geared head units are built for industrial applications rather than hobbiests, and would not sell if they exhibit this flaw. The second is that because they are built more robustly and cost much more, they are priced in a range where the buyer would be more focused on long life under constant use rather than a cheap purchase price.

From my twiddling with the offerings in the lower end of the market (under $800), I have found two models where three display units in three different stores have been free of the problem, other models I have checked have had from half to all display models faulty, suggesting that boxed stock would be also.

The test I do is simple, feed the spindle to a point midway between full retraction and full extension, grasp the body of the chuck and try to move it left to right and front to back relative to the head casting, you will probably manage up to half a mil of movement, if you do, just keep on walking, it won't get better. The test won't work at the fully extended or retracted position as the quill (bit that winds up and down supporting the spindle) will be against stops in the head which inhibit movement.

If the unit feels rock solid, check at different extension degrees. if it still feels OK, then consider the model for purchase, but if possible sample a few of the same model at different outlets. You are then testing that the manufacturer can properly machine the head casting and get it right most of the time, the more samples you test, the better your confidence in the manufacturer could be if they all are OK. One good one in one shop and a dud in another suggests that getting the bore right is hit and miss.

When buying I would also be asking the supplier to allow me to test the unit I was buying in store before leaving, or to sell the display unit that I tested and found acceptable.

Here is some info which may help.
For your purposes its simple tool that most small engineering shops could readily knock up for you using a piece of suitably turned silver steel.

Maybe you are close to one of our contributors who may be willing to do this for you.

Grahame

Thank you Malb,

Lots of good advise in your post.

Regards,
Lou

Hello Lou,
I would make a jig with the drill guide carefully reamed to the Dia. of the drill you are using . It would be preferable to harden the guide but if you made it from something like 4140 and made it about 15mm. long it would probably last long enough . I have a range of drills which I have sharpened "clean cut" where the circumference of the drill begins to cut just after the centre has entered the metal (similar to a Spade Bit ). They are ideal for drilling holes in thin meterials. They produce a perfectly round hole. They are also ideal for drilling holes in soft materials like fibre,wood and plastics as they don't grab like normal drills. Their other advantage,which might interest you is that when drilling aluminium there is almost no burr produced when the drill breaks through the metal. Motor oil is ideal to assist with drilling aluminium as aluminium tends to weld itself to the drill if no cutting oil is used.
Regards, Russell